Brush assemblies for dynamoelectric machines



Jan. 11, 1966 P. H. PELTRET 3,229,135

BRUSH ASSEMBLIES FOR DYNAMO-ELECTRIC MACHINES Filed May 31, 1965 2 Sheets-Sheet 1 BRUSH ASSEMBLIES FOR DYNAMO-ELECTRIG MACHINES Filed May 31, 1963 P. H. PELTRET 'Jan. 11, 1966 2 Sheets-Sheet 2 N QM A A V United States Patent 3,229,135 BRUSH ASSEMBLIES FOR DYNAMO- ELECTRIC MACHINES Pierre Henri Peltret, London, England, assignor to C.A.V. Limited, London, England Filed May 31, 1963, Ser. No. 284,733 1 Claim. (Cl. 310244) The object of this invention is to provide a brush assembly for a dynamo-electric machine in a convenient form.

An assembly according to the invention comprises a pivotally mounted arm and an arcuate brush clamped at one end to the free end of the arm, said brush having an arc of curvature struck substantially from the pivot axis of the arm.

In the accompanying drawings:

FIGURE 1 is an end view of a dynamo-electric machine embodying the invention with a part removed for clarity and FIGURE 2 is a side elevation of the machine shown in FIGURE 1 with the sectional portion thereof taken on the line 2-2 of FIGURE 1.

Referring to the drawings there is provided, at one end of the armature 1, a cylindrical and co-axial commutator 2. Bearing on the commutator at equi-angularly spaced points respectively are four brushes 3 each brush being connected to an appropriate point in the electrical circuit of the machine. The brushes are held in position by clamping them respectively to the free ends of four arms 4 pivotally mounted at equi-angularly spaced positions about insulating sleeves 5 having their axes parallel to the axis of the armature. The arrangement is such that in use, when the armature rotates the brushes 3 are trailing with respect to their associated pins. Each arm 4 carries a spring 6 to urge the associated brush into contact with the peripheral surface of the commutator.

In the particular example the sleeves 5 are supported at one end by an annular carrier 7 which is located against axial movement on a step 8 formed in the casing 9 of the machine. At their other ends the sleeves are supported -by further bushes 10 which bear against the cover 11 of the machine. Moreover in order to strengthen the sleeves pins are mounted therein and for one pair of diametrically opposite sleeves these are constituted by through bolts 12 which serve to hold the parts of the machine together and for the other pair of sleeves by pegs 13.

Patented Jan. 11, 1966 ice In order to prevent the area of contact of the brush and the commutator varying, as the brush Wears, and more particularly to prevent the angle of lead (ie the angle between the longitudinal axis of the brush and a radius passing through the point of contact of the brush and the commutator) varying each brush is made of arcuate form and has a radius of curvature struck from a centre coincident with the axis of the arm in which it is clamped so that during the life of the brush both the area of contact and the angle of lead remain constant. Moreover a short straight portion is provided at one end of the brush to facilitate the clamping of the brush to the arm.

In the example described above each brush is pivotally mounted about an axis parallel to the armature of the machine. It will be understood that if a face type commutator is used each brush assembly will be pivoted about an axis at right angles to the axis of the machine and parallel to a radius of the disc passing through a point of contact of the brush and commutator.

Although the brushes herein described have been of the trailing type this particular construction is equally useful Where brushes of the leading type are used.

I claim:

A dynamo-electric machine comprising a casing, a rotor structure including a commutator rotatable within the casing, an end closure member for the casing, a through bolt extending axially within the casing for retaining said end closure member on the casing, an elec trically insulating sleeve mounted about a portion of said through bolt adjacent the commutator, a pair of hollow electrically insulating carriers mounted on the through bolt at opposite ends of said sleeve respectively, said carriers being located within the casing and serving to locate said sleeve on the through bolt, an arm pivotally mounted about said sleeve, an arcuate brush secured to the free end of said arm, said brush having an arc of curvature struck from the pivot axis of said arm and having a short straight portion about which it is clamped to the arm.

References Cited by the Examiner UNITED STATES PATENTS ORIS L. RADER, Primary Examiner.

MILTON O. HIRSHFIELD, Examiner. 

